Toll-like receptor (TLR) expression in rat gingival epithelium. mRNA from rat gingiva was analyzed for the expression of TLR-2, -3, -4, -5, -6, -7 and -9. The only positive signals obtained by gel electrophoresis were for TLR-3 and -4 (shown). Bone marrow (BM) is included as the positive control for TLRs (positive signals were observed for all TLRs; data not shown), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was included as a housekeeping gene.